Many internal combustion engines use fuel injectors to direct the flow of fuel into a combustion chamber. To adjust the amount of fuel into a combustion chamber, it is common to design the diameter of the seat to be larger, to design the needle or plunger to lift further from a seat, or to open a fuel injector for a longer period.
Changing the seat diameter creates multiple difficulties. For example, as the seat diameter grows, the outside diameter of the fuel injector needs increased disproportionately because the fuel injector forms a pressure vessel, which means that increasing the outside diameter of the fuel injector also requires an increase in the wall thickness of the fuel injector. The increased wall thickness requires additional diameter of the fuel injector specifically to accommodate the increased wall thickness. An increased nozzle seat diameter may also require an increased plunger diameter to maintain the plunger response. Increasing the size of these components can lead to a reduced speed of operation of the fuel injector. It may not be possible in some engines to modify the diameter of a fuel injector because of space considerations.
Changing the lift distance of the plunger can undesirably affect the response speed of the fuel injector. Increasing the lift distance may also result in increased injector-to-injector fueling variability, which is highly undesirable as fueling consistency is important for engine efficiency.
Opening a fuel injector for a longer period to increase the amount of fuel delivered may cause problems with other aspects of engine operation. For example, extending the length of fuel injection may interfere with combustion and exhaust timing. Therefore, increasing the amount of fuel delivered by increasing the length of time a fuel injector is open may not be possible.
Thus, there is a need to increase fuel flow under circumstances that would limit changing the distance a needle or plunger travels, under circumstances that would limit the size of an injector seat, and under circumstances that would limit the length of time an injector is open.